It has long been known that the fluid flow characteristics of an intake manifold can dramatically impact the operational performance of an internal combustion engine thus affecting the response of such engine to different driving conditions. For a given combustive fuel mixture, such as a mixture of gasoline or alcohol with air or nitrous oxide, it is known that the horsepower output of an engine is in direct proportion to the volume of combustive fuel mixture delivered to the engine's cylinders during each power cycle thereof. While it is known, and in certain applications common, to super charge or turbo charge an engine to increase the quantity of fuel product in a cylinder fill during the power cycle, in normal applications, it is the flow dynamics of the carbureting and intake system that determine the efficiency of the delivery of the fuel product mass during the product cycle.
Some of the variables which affect the flow dynamics include the flow capacity of the carburetor, the size of the carburetor outlet, including any restrictions thereof, the size of the intake manifold, or injector or throttle body inlet opening, the volumetric size of the manifold plenum chamber, the cross sectional area of the intake runners and the size of the combustion cylinder inlet as defined by the smaller of the cylinder intake port and runner outlet opening. There are many interrelationships among these variables, and it is often necessary, for peak performance, that these variables be tuned as closely as possible to one another. In these applications, it is desirable to increase volumetric air flow while decreasing any backflow in the intake manifold caused either by turbulence, dead air spaces, or through reverse flow pulses caused by the exhaust stroke of the cylinder during that interval when both intake and exhaust valves are open. The proper timing of the fuel mixture flow can result in reducing turbulence through stable flow and can create inertial filling of the combustion cylinders to increase power.
It is further known that the performance demands on an engine may dictate the desirable flow characteristics of the intake manifold. For example, where maximum speed is sought for the vehicle powered by the engine, a narrow power band having a higher peak power but narrower operative range is desirable. This would be the case where a race car driver seeks to qualify for a race by posting the highest possible lap time. On the other hand, in an actual race numerous vehicles populate the track., different driving situations are encountered. Here, a wider power band is desired even though such wider power band sacrifices the peak power. Accordingly, many race mechanics find it necessary to have a plurality of different intake manifolds on hand for a given engine in order to obtain different results. This procedure is costly, cumbersome, and lacking in flexibility of adjustment.
The need for better intake manifolds useful in racing applications has been recognized in the past, and attempts have been made to improve the flow characteristics of intake manifolds. One such example is found in Morris U.S. Pat. No. 4,109,619 issued August 29, 1978. In this patent, an adapter plate mounts across the manifold inlet opening between the manifold and the outlet of the carbureting device, and a contour block insert is mounted to the adapter plate and downwardly depends into the interior of the plenum chamber. The adapter plate has a plurality of openings which correspond to the runners of the intake manifold, and the contour block attempts to provide contour surfaces to direct the flow of the fuel mixture toward the intake runners. Different contour block inserts may be employed with this adapter plate.
Another intake manifold apparatus is described in Shaffer U.S. Pat. No. 4,210,107 issued July 1, 1980. In the Shaffer patent, linear runners form passageways which convey the fuel mixture from the manifold plenum chamber to the intake ports of each combustion cylinder. Each such passageway has a false side wall formed by a movable panel which moves radially within the passageway so as to alter its effective cross section. This device attempts to match the amount of fuel mixture flow which the cylinder heads and the intake manifold will flow based upon the revolutions per minute and torque on the engine.
Another device constructed to permit modification of the intake manifold is described in Szabo, et al. U.S. Pat. No. 4,279,224 issued July 29, 1981. Here, the manifold apparatus is separated into a valley cover section and a plenum/intake runner section. The engine valley cover section is provided with an integral coolant crossover and distributor mountings so that it may be secured to the engine. The plenum/intake runner section may then be removably mounted to the engine valley section so that differently configured plenum chamber/intake runner sections may be used with a common engine valley section and that these may be interchanged without removing the entire intake manifold apparatus. While this device has advantage over changing the entire intake manifold, it nonetheless remains cumbersome and expensive since numerous/intake runner plenum chamber units must be maintained on hand to give any flexibility in varying of the flow dynamics for the engine.
Despite the advancements described in the above-referenced patents, there remains a need for an improved intake manifold apparatus that permits flexibility in adjustment of flow characteristics. There remains a further need for intake manifold apparatus which may be mounted on different engines of the same block size and which may be adjusted to provide different flow characteristics for such different engines. There is a further need for an adjustable manifold apparatus which can be used for racing applications and street driving and allows increased efficiency and power for an internal combustion engine.